JP2022018218A - Management device, power storage device, and management method of power storage element - Google Patents

Abstract

To provide a management device, a power storage device, and a management method that suppress deterioration of the estimation accuracy of the state of a power storage element not only when the characteristics of a current sensor change over time but also when the characteristics of the current sensor suddenly change.SOLUTION: In a power storage device 15, a BMU 31 of a battery cell 30A includes a current sensor 33 connected in series with the battery cell 30A and a management unit 37. The management unit 37 executes a correction process of correcting a current value measured by the current sensor 33 on the basis of the correction value, an estimation process of estimating the SOC of the battery cell 30A on the basis of the current value corrected by the correction process, an integration process of integrating a correction value P according to the execution of the correction process, a full charge reset of reducing an error accumulated in the estimated value of SOC when an integrated value integrated in the integration process reaches a first threshold (5% of the current SOC), and a change process of changing the correction value according to the current value measured by the current sensor 33.SELECTED DRAWING: Figure 5

Description

The present invention relates to a power storage element management device, a power storage device, and a management method.

Conventionally, in a management device that manages a power storage element such as a lithium ion secondary battery, a current sensor for measuring the charge / discharge current of the power storage element is provided, the current value measured by the current sensor is corrected, and the corrected current value is used. There is known one that estimates the state of the power storage element (see, for example, Patent Document 1).
Specifically, the charge depth calculation circuit described in Patent Document 1 includes a current detection unit that detects a current flowing through the power storage device, and a voltage acquisition unit that acquires the terminal voltage of the power storage device. The charge depth calculation circuit corrects the current value detected by the current detection unit and integrates the corrected current value to calculate the charge depth (corresponding to the state of the power storage element) of the power storage device. The charge depth calculation circuit estimates the terminal voltage from the calculated charge depth, and corrects the current value so as to reduce the difference between the estimated terminal voltage and the terminal voltage acquired by the voltage acquisition unit.

Japanese Patent Application No. 2009-109269

The characteristics of the current sensor may change with use. The characteristics of the current sensor may change over time even when no current flows. For convenience, in the following description, the change in the characteristics of the current sensor with use and the change over time are collectively referred to as the change in the characteristics of the current sensor over time. If the characteristics of the current sensor change over time, the accuracy of estimating the state of the power storage element deteriorates. This has not been studied in the invention described in Patent Document 1 described above.

The present specification discloses a technique for suppressing deterioration of the estimation accuracy of the state of the power storage element not only when the characteristics of the current sensor change over time but also when the characteristics of the current sensor suddenly change. do.

It is a management device for a power storage element, and includes a current sensor connected in series with the power storage element and a management unit. The management unit calculates a current value measured by the current sensor based on a correction value. The correction process for correction, the estimation process for estimating the state of the power storage element based on the current value corrected by the correction process, the integration process for integrating a predetermined value according to the execution of the correction process, and the integration process. When the integrated value integrated in is reached the first threshold value, the reduction process for reducing the error accumulated in the estimated value of the state, and the predetermined value and the predetermined value according to the physical quantity related to the characteristic change of the current sensor. A change process for changing at least one of the first thresholds is executed.

It is possible to suppress deterioration of the estimation accuracy of the state of the power storage element not only when the characteristics of the current sensor change over time but also when the characteristics of the current sensor suddenly change.

Schematic diagram of the vehicle according to the first embodiment Schematic diagram of alternator, electrical load and power system An exploded perspective view of the power storage device Plan view of power storage element Sectional drawing of line AA shown in FIG. 4A Block diagram showing the electrical configuration of the power storage device Schematic diagram showing the configuration of the current sensor Graph of integrated value of correction value Graph of voltage value and current value when charging the power storage device Flow chart of SOC estimation, SOC full charge reset and correction value change Graph of integrated value of correction value according to Embodiment 2 A graph showing the relationship between SOC and OCV of a power storage element having a plateau region.

(Outline of this embodiment)
(1) According to one aspect of the present invention, the management device for the power storage element includes a current sensor connected in series with the power storage element and a management unit, and the management unit measures the current sensor. A correction process for correcting the corrected current value based on the correction value, an estimation process for estimating the state of the power storage element based on the current value corrected by the correction process, and a predetermined value according to the execution of the correction process. It is related to the integration process for integrating the current sensor, the reduction process for reducing the error accumulated in the estimated value of the state when the integrated value integrated in the integration process reaches the first threshold value, and the characteristic change of the current sensor. The change process of changing at least one of the predetermined value and the first threshold value according to the physical quantity to be performed is executed.

According to the above management device, the characteristics of the current sensor are changed over time by investigating the tendency of the characteristics of the current sensor over time and setting a correction value, and then correcting the current value based on the correction value. Even if it changes to, the current value can be corrected with some accuracy. Therefore, even if the characteristics of the current sensor change with time, it is possible to prevent the estimation accuracy of the state of the power storage element from deteriorating.
However, since the above-mentioned correction value is determined based on past experiments and does not necessarily represent an actual characteristic change, an error may be accumulated in the estimated value of the state of the power storage element. According to the above management device, a predetermined value is integrated according to the execution of the correction process, and when the integrated value of the predetermined value reaches the first threshold value, the error accumulated in the estimated value of the state of the power storage element is reduced. Since the processing is executed, it is possible to suppress the deterioration of the estimation accuracy of the state of the power storage element due to the accumulation of errors.

The characteristics of the current sensor not only change over time, but may also change suddenly due to a large current or temperature rise. Sudden change means that the range of change in characteristics per unit time is larger than the change over time. Examples of causes of large current and temperature rise include an external short circuit and a failure of a charger for charging a power storage element. The correction value set based on the characteristic change over time is set assuming that the characteristic of the current sensor changes slowly with the passage of time. Therefore, if the characteristic change suddenly occurs, The current value cannot be corrected properly. Therefore, the error accumulated in the estimated value of the state of the power storage element becomes large.

However, as described above, the management device executes the reduction process when the integrated value of the predetermined value reaches the first threshold value. In the reduction process, even an error accumulated due to a sudden change in characteristics is reduced. Therefore, even if a sudden change in characteristics occurs, the error is reduced by the reduction process over time. However, the estimation accuracy is temporarily deteriorated until the reduction process is executed.

Some management devices are equipped with means for calibrating the current sensor. In that case, if calibration is performed regularly, the measurement error of the current sensor can be suppressed even if the characteristics suddenly change. However, when the interval at which calibration is performed is long, such as once every 7 days, the measurement error of the current value becomes large until the next calibration is performed, and it cannot be ignored as a factor of estimation error of the state.

Whether or not a sudden characteristic change of the current sensor has occurred can be inferred from the physical quantity related to the characteristic change of the current sensor. According to the above management device, at least one of the predetermined value and the first threshold value is changed according to the physical quantity related to the characteristic change of the current sensor. Therefore, by changing at least one of the predetermined value and the first threshold value so that the time until the integrated value of the predetermined value reaches the first threshold value is shortened, the reduction process is executed with high frequency. become. As a result, it is possible to shorten the period during which the estimation accuracy of the state of the power storage element temporarily deteriorates.
Therefore, according to the above management device, it is possible to suppress deterioration of the estimation accuracy of the state of the power storage element not only when the characteristics of the current sensor change over time but also when the characteristics of the current sensor suddenly change. can.

In the above-mentioned "integration process for accumulating predetermined values according to the execution of the correction process", if the number of times the correction process is executed and the number of times the predetermined values are integrated match, the correction process is not necessarily executed once. The process is not limited to the process of accumulating a predetermined value once each time. For example, the predetermined value may be integrated twice every time the correction process is executed twice. The number of times the correction process is executed and the number of times the predetermined values are integrated may be substantially the same, and may not necessarily be completely the same.

The "integration process for accumulating predetermined values according to the execution of the correction process" is not limited to adding predetermined values, and includes other methods having substantially the same meaning. For example, a predetermined value may be subtracted (corresponding to integration) from a certain initial value according to the execution of the correction processing, and the reduction processing may be executed when the subtracted value (corresponding to the integrated value) reaches the first threshold value. .. Alternatively, subtraction can be rephrased as adding a negative value.

(2) According to one aspect of the present invention, the predetermined value is the correction value, and the management unit may change the correction value in the change processing.

In the change process, the predetermined value may be changed or the first threshold value may be changed according to the change in the characteristics of the current sensor. However, if the predetermined value is a correction value, the predetermined value may be changed. Compared with the case of changing the threshold value of 1, there are the following advantages.
When the predetermined value is a correction value, changing the predetermined value means changing the correction value. When the correction value is changed, the current value is corrected in the correction process based on the changed correction value, so that the accuracy of the correction in the correction process is improved as compared with the case where the first threshold value is changed. Therefore, it is possible to further suppress the deterioration of the estimation accuracy of the state of the power storage element due to the change in the characteristics of the current sensor over time.

(3) According to one aspect of the present invention, the state may be a charging state of the power storage element.

According to the above management device, the estimation accuracy of the charge state (SOC: System of Chareg) of the power storage element not only when the characteristics of the current sensor change over time but also when the characteristics of the current sensor suddenly change. Can be suppressed from getting worse.

(4) According to one aspect of the present invention, the power storage element may have a plateau region in which the change in voltage with respect to the change in charge state is small.

As shown in FIG. 11, some power storage elements have a plateau region in which the change in the open circuit voltage (OCV: Open Circuit Voltage) of the power storage element with respect to the change in the state of charge (SOC) is small. Specifically, the plateau region is a region in which the amount of change in OCV with respect to the amount of change in SOC is 2 [mV /%] or less.
In the case of a power storage element that does not have a plateau region, the SOC can be estimated accurately from the OCV. Therefore, by estimating the SOC from the OCV, the SOC can be estimated accurately even if the characteristics of the current sensor change. On the other hand, since it is difficult to accurately estimate the SOC from the OCV in the power storage element having a plateau region, the SOC is usually estimated based on the current value. In such a power storage element, if the characteristics of the current sensor change, the estimation accuracy of the SOC deteriorates. Therefore, other than the method of estimating the SOC from the OCV, the deterioration of the estimation accuracy of the SOC when the characteristics of the current sensor changes is suppressed. A method was desired.
According to the above management device, even if the storage element is difficult to estimate the SOC from the OCV, it is possible to suppress the deterioration of the SOC estimation accuracy due to the change in the characteristics of the current sensor. Therefore, the above management device is particularly useful in the case of a power storage element having a plateau region.

(5) According to one aspect of the present invention, in the reduction process, the power storage element is charged to a predetermined charging state, and the estimated value of the charging state estimated by the estimation process is used as the value of the predetermined charging state. It may be a process of updating to.

According to the above management device, the power storage element is charged to a predetermined charging state, and the estimated value of the charging state estimated by the estimation process is updated with the value of the predetermined charging state, so that it is accumulated in the estimated value of the charging state. The error can be reduced.

(6) According to one aspect of the present invention, the physical quantity is a current value measured by the current sensor, and the management unit has a current value equal to or higher than a second threshold value by the current sensor in the change process. When measured, at least one of the predetermined value and the first threshold value may be changed.

The characteristics of the current sensor may change suddenly when a large current (current whose current value is equal to or greater than the second threshold value) flows. According to the above management device, when a current value equal to or higher than the second threshold value is measured by the current sensor, at least one of the predetermined value and the first threshold value is changed, so that a large current flows and the characteristics of the current sensor are sudden. When the value changes to, it is possible to prevent the estimation accuracy of the state of the power storage element from deteriorating.

(7) According to one aspect of the present invention, the physical quantity is a current value measured by the current sensor, and the management unit has a third threshold value or more and a fourth threshold value by the current sensor in the change process. When a current value less than the threshold value is continuously measured for a predetermined time or longer, at least one of the predetermined value and the first threshold value may be changed.

The characteristics of the current sensor are sudden not only when an abnormally large current flows, but also when a large current in the normal range (current whose current value is greater than or equal to the third threshold value and less than the fourth threshold value) flows for a long time. It may change. According to the above management device, when the current value of the third threshold value or more and less than the fourth threshold value is continuously measured for a predetermined time or longer, at least one of the predetermined value and the first threshold value is changed. Therefore, even if the characteristics of the current sensor suddenly change due to the large current flowing in the normal range for a long time, it is possible to suppress the deterioration of the estimation accuracy of the state of the power storage element.

(8) According to one aspect of the present invention, the temperature sensor for measuring the temperature of the power storage element is provided, the physical quantity is the temperature measured by the temperature sensor, and the management unit is described in the change process. When the temperature of the fifth threshold value or higher is measured by the temperature sensor, at least one of the predetermined value and the first threshold value may be changed.

When a large current flows, the temperature of the power storage element rises, so if the temperature of the power storage element rises abnormally (more than or equal to the fifth threshold value), it is highly possible that the characteristics of the current sensor have changed significantly. According to the above management device, when the temperature sensor measures a temperature equal to or higher than the fifth threshold value, at least one of the predetermined value and the first threshold value is changed, so that a large current flows and the characteristics of the current sensor suddenly change. Even if it changes, it is possible to prevent the estimation accuracy of the state of the power storage element from deteriorating.

(9) According to one aspect of the present invention, the current sensor has a resistor, and the current value may be measured using the resistor.

In a current sensor that measures a current value using a resistor, the resistance value of the resistor (characteristics of the current sensor) may change suddenly due to a large current or temperature rise. According to the above management device, even if the resistance value of the resistor suddenly changes due to a large current or a temperature rise, it is possible to prevent the estimation accuracy of the state of the power storage element from deteriorating.

(10) According to one aspect of the present invention, the power storage device includes a power storage element and the management device according to any one of claims 1 to 9.

According to the above-mentioned power storage device, it is possible to suppress deterioration of the estimation accuracy of the state of the power storage element not only when the characteristics of the current sensor change with time but also when the characteristics of the current sensor suddenly change.

(11) According to one aspect of the present invention, the method of managing the power storage element includes a correction step of correcting the current value measured by the current sensor connected in series with the power storage element based on the correction value, and the above-mentioned correction step. An estimation step that estimates the state of the power storage element based on the current value corrected in the correction step, an integration step that integrates a predetermined value according to the execution of the correction step, and an integration value integrated in the integration step When the first threshold is reached, a reduction step of reducing the error accumulated in the estimated value of the state, and at least one of the predetermined value and the first threshold depending on the physical quantity related to the characteristic change of the current sensor. Includes change steps and changes.

According to the above management method, it is possible to suppress deterioration of the estimation accuracy of the state of the power storage element not only when the characteristics of the current sensor change with time but also when the characteristics of the current sensor suddenly change.

The invention disclosed herein can be realized in various aspects such as devices, methods, computer programs for realizing the functions of these devices or methods, recording media on which the computer programs are recorded, and the like.

<Embodiment 1>
The first embodiment will be described with reference to FIGS. 1 to 9. In the following description, the reference numerals of the drawings may be omitted for the same constituent members except for some parts.

(1) Vehicle power supply system The vehicle 1 shown in FIG. 1 is an engine-driven vehicle, and is equipped with an alternator 11, an electric load 12, and a power supply system 13, which are vehicle generators. The electric load 12 is rated at 12V. Examples of the electric load 12 include an engine starting device such as a starter motor, auxiliary equipment (air conditioner, audio, car navigation), and the like. The power supply system 13 supplies electric power to the engine starting device and auxiliary equipment.

As shown in FIG. 2, the power supply system 13 includes a vehicle ECU 14 (electronic control unit: Electronic Control Unit) and a power storage device 15. The vehicle ECU 14 includes a CPU 14A, a RAM 14B, a ROM 14C, and the like, and is communicably connected to the power storage device 15.

(2) Configuration of power storage device As shown in FIG. 3, the power storage device 15 includes an accommodating body 71. The housing 71 includes a main body 73 made of a synthetic resin material and a lid 74. The main body 73 has a bottomed tubular shape. The main body 73 includes a bottom surface portion 75 and four side surface portions 76. An upper opening 77 is formed at the upper end portion by the four side surface portions 76.

The accommodating body 71 accommodates an assembled battery composed of a plurality of battery cells 30A (an example of a power storage element) and a circuit board unit 72. The circuit board unit 72 is arranged on the upper part of the assembled battery.
The lid 74 closes the upper opening 77 of the body 73. An outer peripheral wall 78 is provided around the lid 74. The lid 74 has a substantially T-shaped protrusion 79 in a plan view. The external terminal 80P of the positive electrode is fixed to one corner of the front portion of the lid 74, and the external terminal 80N of the negative electrode is fixed to the other corner.

The battery cell 30A is a secondary battery that can be repeatedly charged and discharged, and specifically, a lithium ion secondary battery. More specifically, the battery cell 30A is a lithium ion secondary battery having a plateau region in which the change in OCV is relatively small with respect to the change in SOC. Examples of the lithium ion secondary battery having a plateau region include an iron-based lithium ion secondary battery in which iron is contained in the positive electrode active material. Examples of the iron-based lithium ion secondary battery include an LFP / Gr-based lithium ion secondary battery containing LiFePO4 (lithium iron phosphate) as the positive electrode active material and Gr (graphite) as the negative electrode active material.

As shown in FIGS. 4A and 4B, the battery cell 30A contains an electrode body 83 together with a non-aqueous electrolyte in a rectangular parallelepiped case 82. The case 82 has a case body 84 and a lid 85 that closes an opening above the case body 84.
Although not shown in detail, the electrode body 83 is porous between the negative electrode element in which the negative electrode active material is applied to the base material made of copper foil and the positive electrode element in which the positive electrode active material is applied to the base material made of aluminum foil. A separator made of the above resin film is arranged. All of these are band-shaped, and the negative electrode element and the positive electrode element are wound flat so as to be accommodated in the case body 84 with the positions of the negative electrode element and the positive electrode element shifted to the opposite sides in the width direction with respect to the separator. There is.

The positive electrode terminal 87 is connected to the positive electrode element via the positive electrode current collector 86, and the negative electrode terminal 89 is connected to the negative electrode element via the negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 include a flat plate-shaped pedestal portion 90 and a leg portion 91 extending from the pedestal portion 90. A through hole is formed in the pedestal portion 90. The leg 91 is connected to a positive electrode element or a negative electrode element. The positive electrode terminal 87 and the negative electrode terminal 89 include a terminal main body portion 92 and a shaft portion 93 protruding downward from the center portion of the lower surface thereof. Among them, the terminal body portion 92 and the shaft portion 93 of the positive electrode terminal 87 are integrally molded of aluminum (single material). In the negative electrode terminal 89, the terminal body portion 92 is made of aluminum and the shaft portion 93 is made of copper, and these are assembled. The terminal main body 92 of the positive electrode terminal 87 and the negative electrode terminal 89 is arranged at both ends of the lid 85 via a gasket 94 made of an insulating material, and is exposed to the outside from the gasket 94.

As shown in FIG. 4A, the lid 85 has a pressure release valve 95. The pressure release valve 95 is located between the positive electrode terminal 87 and the negative electrode terminal 89. The pressure release valve 95 opens when the internal pressure of the case 82 exceeds the limit value to reduce the internal pressure of the case 82.

(3) Electrical Configuration of Power Storage Device As shown in FIG. 5, the power storage device 15 includes an assembled battery 30, a BMU 31 (an example of a management device), and a communication connector 32. As will be described in detail later, the BMU 31 includes a current sensor 33. The assembled battery 30 and the current sensor 33 are connected in series via power lines 34P and 34N. The power line 34P is a power line that connects the external terminal 80P of the positive electrode and the positive electrode of the assembled battery 30. The power line 34N is a power line that connects the external terminal 80N of the negative electrode and the negative electrode of the assembled battery 30.

In the assembled battery 30, 12 battery cells 30A are connected in 3 parallels and 4 in series. In FIG. 3, three battery cells 30A connected in parallel are represented by one battery symbol.
The BMU 31 includes a current sensor 33, a voltage detection circuit 35, a temperature sensor 36, and a management unit 37. The voltage detection circuit 35 and the management unit 37 are mounted on the circuit board unit 72 (see FIG. 4).

The current sensor 33 is located on the negative electrode side of the assembled battery 30 and is provided on the power line 34N of the negative electrode. The current sensor 33 measures the charge / discharge current [A] of the assembled battery 30 and outputs it to the management unit 37. The configuration of the current sensor 33 will be described later.
The voltage detection circuit 35 is connected to both ends of each battery cell 30A by a signal line. The voltage detection circuit 35 measures the battery voltage [V] of each battery cell 30A and outputs it to the management unit 37. The total voltage [V] of the assembled battery 30 is the total voltage of the four battery cells 30A connected in series.
The temperature sensor 36 is a contact type or a non-contact type, and measures the temperature [° C.] of the battery cell 30A and outputs it to the management unit 37. Although omitted in FIG. 5, two or more temperature sensors 36 are provided. Each temperature sensor 36 detects the temperature of the battery cells 30A different from each other.

The management unit 37 includes a microcomputer 37A in which a CPU, RAM, and the like are integrated into a single chip, a storage unit 37B, and a communication unit 37C. The storage unit 37B is a storage medium in which data can be rewritten, and various programs, a correction value P described later, and the like are stored. The microcomputer 37A manages the power storage device 15 by executing a program stored in the storage unit 37B. The communication unit 37C is a circuit for the BMU 31 to communicate with the vehicle ECU 14.
The communication connector 32 is a connector to which a communication cable for the BMU 31 to communicate with the vehicle ECU 14 is connected.

The configuration of the current sensor 33 will be described with reference to FIG. The current sensor 33 has a shunt resistor 33A (an example of a resistor) connected in series with the battery cell 30A, and a detection circuit 33B for detecting the potential difference between both ends of the shunt resistor 33A. The detection circuit 33B detects the potential difference between both ends of the shunt resistance 33A, and calculates the current value from the resistance value and the potential difference of the shunt resistance 33A according to Ohm's law.

The resistance value of the shunt resistor 33A changes with time, and may also change suddenly due to a large current or an abnormal temperature rise.
For example, when the engine of the vehicle 1 is started, a large current flows from the power storage device 15 to the engine starting device. The large current at that time is about 600 A to 700 A, which is a large current in the normal range. In the case of a large current in the normal range, it is unlikely that the resistance value of the shunt resistor 33A will change suddenly for a short time. On the other hand, in the power storage device 15, an abnormally large current may flow due to a failure of the alternator 11 or an external short circuit. The current value of the current flowing due to the external short circuit is, for example, 1500 A or more, which is an abnormally large current. When such an abnormally large current flows, the resistance value of the shunt resistor 33A may change suddenly even for a short time.

Even if the current is large in the normal range, the resistance value may change suddenly due to the flow over a long period of time. For example, the starter motor included in the engine starter may be locked (non-rotatable) due to a failure. In that case, a large current may flow from the power storage device 15 to the engine starting device for a long time in order to rotate the starter motor. The large current at this time is a large current in the normal range, but the resistance value of the shunt resistor 33A may suddenly change due to the flow over a long period of time.

When an abnormally large current flows or when a large current in the normal range flows for a long time, the temperature of the battery cell 30A also rises abnormally. Therefore, if the temperature measured by the temperature sensor 36 is abnormally high, or if the abnormally high temperature continues for a long time, it can be determined that the resistance value of the shunt resistor 33A has suddenly changed.

(4) SOC estimation, SOC full charge reset, and change of correction value The management unit 37 estimates the SOC (state, an example of the charging state) of the power storage device 15 by the current integration method (an example of the estimation process and the estimation step). .. The current integration method is a method in which a current value is measured by a current sensor 33 at a predetermined time interval (10 milliseconds or the like), and the SOC is estimated by adding or subtracting the measured current value to an initial value.

As described above, since the resistance value of the shunt resistor 33A changes with time, the estimation accuracy of SOC deteriorates unless the time-dependent change (tendency of characteristic change) of the resistance value is taken into consideration. Therefore, the management unit 37 corrects the current value by adding the correction value P to the current value measured by the current sensor 33 (an example of the correction process and the correction step), and estimates the SOC using the corrected current value. (Example of estimation process and estimation step). The correction value P is determined based on a change over time in the resistance value of the shunt resistor 33A obtained in advance by an experiment. Normally, the resistance value of the shunt resistor 33A changes slowly with the passage of time, so the correction value P is also determined on the assumption that the resistance value changes slowly with the passage of time.

Since the correction value P is determined based on past experiments and does not necessarily represent a change in the actual resistance value, an error may be accumulated in the estimated value of SOC. Therefore, the management unit 37 integrates the correction value P (an example of a predetermined value) according to the execution of the correction process (an example of the integration process and the integration step), and when the integrated value of the correction value P reaches the first threshold value. , Performs a reduction process to reduce the error accumulated in the SOC estimates. Specifically, the management unit 37 according to the first embodiment integrates the correction value P (an example of a predetermined value) into the counter C each time the correction process is executed, and the integrated value of the correction value P reaches the first threshold value. Then, a full charge reset (an example of a reduction process and a reduction step) described later is executed. Counter C is initialized to 0 when a full charge reset is performed.

The above-mentioned first threshold value will be described with reference to FIG. 7. In the case of the example shown in FIG. 7, the first threshold value is a value corresponding to 5% of the current SOC. The management unit 37 executes a full charge reset when the integrated value of the correction value P reaches a value corresponding to 5% of the current SOC. The first threshold is not limited to 5% of the current SOC and can be determined as appropriate. For example, the first threshold value may be a value corresponding to 5% of the total charge capacity of the power storage device 15.

A full charge reset will be described with reference to FIG. In FIG. 8, the solid line 50 shows the current value, and the alternate long and short dash line 51 shows the voltage value. Full charge here does not necessarily mean that the SOC is 100%, but that the battery cell 30A is fully charged to a predetermined SOC (for example, 99.2%) or a predetermined voltage. That is.

When the integrated value of the correction value P reaches the first threshold value, the management unit 37 cooperates with the vehicle ECU 14 to fully charge the power storage device 15. When the power storage device 15 is fully charged, constant current charging (CC charging) is performed until the voltage of the power storage device 15 reaches a predetermined voltage (for example, 3.5V), and when the voltage reaches a predetermined voltage, constant voltage charging (CV charging) is performed. ). In constant voltage charging, the current value gradually decreases, and when the current value decreases to the threshold value I_thr, the battery is fully charged. In the case of the example shown in FIG. 8, the SOC when the current value drops to the threshold value I_thr is 99.2% (an example of a predetermined state of charge). Therefore, when the current value drops to the threshold value I_thr, the management unit 37 updates the SOC estimated by the current integration method to 99.2%. Since the full charge reset is generally highly accurate, the error accumulated in the SOC estimated by the current integration method can be reduced.

The change of the correction value P will be described with reference to FIG. 7. Since the correction value P is determined on the assumption that the resistance value of the shunt resistor 33A changes slowly with the passage of time, the current value cannot be appropriately corrected when the resistance value suddenly changes. If the current value cannot be corrected appropriately, the SOC estimation accuracy will temporarily deteriorate until the next full charge reset is executed. Therefore, the management unit 37 determines whether or not the resistance value of the shunt resistor 33A suddenly changes from the current value (an example of a physical quantity related to the characteristic change of the current sensor 33), and the resistance value suddenly changes. If this is the case, the correction value P is changed so that the time until the integrated value of the correction value P reaches the first threshold value is shortened (an example of the change process and the change step).

Specifically, it is assumed that the resistance value changes significantly at the time point T1. In this case, the management unit 37 changes the correction value P to, for example, twice at the time point T1. In FIG. 7, the solid line 53 is a graph when the correction value P is not changed, and the alternate long and short dash line 54 is a graph when the correction value P is doubled. In the case of the example shown in FIG. 7, when the correction value P is not changed, the integrated value reaches the first threshold value (SOC5%) at the time point T3, whereas when the correction value P is doubled, the time point T3 The first threshold is reached at an earlier point in time T2. Therefore, as compared with the case where the correction value P is not changed (solid line 53), the time until the integrated value of the correction value P reaches the first threshold value is shortened. Therefore, the full charge reset is executed frequently, and it is possible to suppress the deterioration of the SOC estimation accuracy due to the sudden change in the resistance value of the shunt resistor 33A.

With reference to FIG. 9, the flow of SOC estimation, SOC full charge reset, and correction value change will be described. This process is started every time the current value is measured by the current sensor 33 at a predetermined time interval.
In S101, the management unit 37 corrects the current value by adding the correction value P stored in the storage unit 37B to the current value measured by the current sensor 33.
In S102, the management unit 37 estimates the SOC based on the current value corrected in S101. This estimation is performed by the current integration method.

In S103, the management unit 37 determines whether or not the resistance value of the shunt resistor 33A suddenly changes from the current value corrected in S101 (the current value before correction may be used). Specifically, the management unit 37 determines whether or not the following (a) or (b) is satisfied.
(A) Abnormally large current: The measured current value is 1000 A or more. 1000A is an example of the second threshold.
(B) Large current in the normal range continues for a long time: Current values of 600 A or more and less than 1000 A were continuously measured in the latest multiple measurements including this measurement. 600A is an example of a third threshold value, and 1000A is an example of a fourth threshold value.
If (a) or (b) is satisfied, the management unit 37 determines that the resistance value has suddenly changed and proceeds to S104. If neither of them is satisfied, the management unit 37 determines that the resistance value has not changed and proceeds to S105. move on.

In S104, the management unit 37 rewrites the correction value P stored in the storage unit 37B to a double value. Since the correction value P stored in the storage unit 37B is rewritten, the doubled correction value P is used in the next and subsequent executions of this process.
In S105, the management unit 37 adds the correction value P to the counter C that integrates the correction value P. S105 may be executed before S103.

In S106, the management unit 37 determines whether or not the value of the counter C is equal to or greater than the first threshold value, proceeds to S107 if the value is equal to or greater than the first threshold value, and proceeds to S107 if the value is equal to or greater than the first threshold value. To finish.
In S107, the management unit 37 resets the full charge.
In S108, the management unit 37 initializes the counter C to 0.

(5) Effect of the Embodiment According to the BMU 31, the estimation accuracy of the SOC of the battery cell 30A deteriorates not only when the resistance value of the shunt resistor 33A changes with time but also when the resistance value suddenly changes. Can be suppressed.

According to the BMU 31, the predetermined value is the correction value P, and the correction value P is changed according to the sudden change in the resistance value. When the correction value P is changed, the current value is corrected based on the changed correction value P also in the correction process, so that the accuracy of the correction in the correction process is improved as compared with the case where the first threshold value is changed. Therefore, it is possible to further suppress the deterioration of the SOC estimation accuracy of the battery cell 30A due to the change over time in the resistance value of the shunt resistor 33A.

According to BMU31, the state of the battery cell 30A is SOC. According to the BMU 31, it is possible to suppress deterioration of the SOC estimation accuracy not only when the resistance value of the shunt resistor 33A changes over time but also when the resistance value of the shunt resistor 33A suddenly changes.

According to the BMU 31, even a battery cell 30A having a plateau region (a battery cell 30A in which it is difficult to estimate SOC from OCV) can suppress deterioration of SOC estimation accuracy due to a change in the resistance value of the shunt resistor 33A. Therefore, the BMU 31 is particularly useful in the case of a battery cell 30A having a plateau region.

According to the BMU 31, when the integrated value of the correction value P reaches the first threshold value, the full charge reset is performed, so that the error accumulated in the estimated value of the SOC can be reduced.

According to BMU31, the correction value P is changed when a large current of 1000 A or more is measured by the current sensor 33, so even if an abnormally large current flows and the resistance value of the shunt resistor 33A suddenly changes, the SOC is estimated. Deterioration of accuracy can be suppressed.

According to the BMU 31, the correction value P is changed when a large current of 600 A or more and less than 1000 A is continuously measured by the current sensor 33 for a predetermined time or longer. Even if the resistance value of is suddenly changed, the deterioration of the estimation accuracy of SOC can be suppressed.

According to the BMU 31, the current sensor 33 has a shunt resistor 33A, and the shunt resistor 33A is used to measure the current value. In the current sensor 33 that measures the current value using the shunt resistance 33A, the resistance value of the shunt resistance 33A (characteristic of the current sensor 33) may suddenly change due to a large current or an abnormal temperature rise. According to the BMU 31, even if the resistance value of the shunt resistor 33A suddenly changes due to a large current or an abnormal temperature rise, deterioration of the SOC estimation accuracy can be suppressed.

<Embodiment 2>
The second embodiment will be described with reference to FIG. In the above-described first embodiment, a case where the correction value P is doubled when an abnormally large current is detected has been described as an example. On the other hand, in the second embodiment, the correction value P is not doubled, but the first threshold value is reduced.

This will be specifically described with reference to FIG. In FIG. 10, the time point T1 is the time point when an abnormally large current is detected. As shown in FIG. 10, the BMU 31 reduces the first threshold when it detects an abnormally large current. Specifically, for example, the BMU 31 sets an intermediate value between the integrated value (counter C value) at the time point T1 and the first threshold value before the change as the first threshold value after the change. As a result, the next full charge reset is executed at substantially the same timing as when the correction value P is doubled. The changed first threshold value can be appropriately selected and is not limited to the above-mentioned intermediate value.

According to the BMU 31 according to the second embodiment, when it is determined from the current value that a sudden characteristic change of the current sensor 33 has occurred, the integrated value of the correction value P is the first by reducing the first threshold value. The time required to reach the threshold value of can be shortened. Therefore, the full charge reset is executed frequently, and it is possible to suppress the deterioration of the SOC estimation accuracy due to the sudden change in the resistance value of the shunt resistor 33A.

<Other embodiments>
The present invention is not limited to the embodiments described above and the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

(1) In the above embodiment, the process of adding the correction value P to the current value is exemplified as the correction process, but the correction process is not limited to this. For example, the correction process may be a process of multiplying the current value by the correction value.

(2) In the above embodiment, SOC is exemplified as the state of the power storage element, but the state is not limited to SOC. For example, the state may be SOH (State Of Health) indicating a health state or a deterioration state.

(3) In the first embodiment, the case where it is determined that the resistance value has changed significantly when an abnormally large current is measured or when a large current in the normal range continues for a long time is illustrated. On the other hand, when the temperature sensor 36 measures a temperature equal to or higher than the fifth threshold value (an example of a physical quantity related to a change in the characteristics of the current sensor 33), it is determined that the resistance value has changed significantly, and the correction value P is changed. You may. By doing so, even if a large current flows and the characteristics of the current sensor 33 change significantly, deterioration of the SOC estimation accuracy can be suppressed.

(4) In the above embodiment, the case where the correction value P is integrated as a predetermined value each time the correction process is executed is illustrated, but the predetermined value is not limited to the correction value and may be any value. For example, if the correction value P is integrated 10 times and reaches, for example, 5% of the SOC, the predetermined value may be set to 1, and when the integrated value reaches 10, a full charge reset may be executed. The integrated value in this case corresponds to the number of times the correction process is executed.

(5) In the above embodiment, the lithium ion secondary battery is exemplified as the battery cell 30A, but the battery cell 30A is not limited to the lithium ion secondary battery. For example, the battery cell 30A may be a capacitor with an electrochemical reaction.
In the above embodiment, the lithium ion secondary battery having a plateau region is exemplified as the lithium ion secondary battery, but the lithium ion secondary battery is not limited to the one having a plateau region.
In the above embodiment, an iron-based lithium ion secondary battery is exemplified as the lithium ion secondary battery having a plateau region, but the lithium ion secondary battery having a plateau region is not limited to the iron-based lithium ion secondary battery.
In the above embodiment, the LFP / Gr-based lithium-ion secondary battery is exemplified as the iron-based lithium-ion secondary battery, but the iron-based lithium-ion secondary battery is not limited to the LFP / Gr-based lithium-ion secondary battery. ..

(6) Although the current sensor 33 provided with the shunt resistor 33A is exemplified in the above embodiment, the current sensor 33 may be, for example, a hall sensor.

(7) In the above embodiment, the engine-driven vehicle is exemplified as the vehicle 1, but the vehicle 1 is not limited to this. For example, the vehicle 1 may be a hybrid vehicle, an electric vehicle, a forklift traveling by an electric motor, or an automatic guided vehicle (AGV).
In the above embodiment, the power storage device 15 mounted on the vehicle is exemplified, but the power storage device 15 is not limited to the one mounted on the vehicle. For example, the power storage device 15 may be a power storage device used in an uninterruptible power supply (UPS), or may be a power storage device that stores power generated by photovoltaic power generation.

(8) In the above embodiment, a case where a predetermined value (correction value P) is integrated once in S105 (integration processing) every time S101 (correction processing) is executed has been described as an example. However, the integration process is not necessarily limited to the process of integrating the predetermined value once for each execution of the correction process, as long as the number of times the correction process is executed and the number of times the predetermined value is integrated match. .. For example, the predetermined value may be integrated twice every time the correction process is executed twice. The number of times the correction process is executed and the number of times the predetermined values are integrated may be substantially the same, and may not necessarily be completely the same.

(9) In the above embodiment, the battery cell 30A mounted on the vehicle 1 as the power storage element (battery cell 30A) has been described as an example, but the power storage element is not limited to that mounted on the vehicle. For example, the power storage element may be mounted on a small electric product.

(10) In the above embodiment, the correction value P is added to the counter C every time the current value is corrected based on the correction value P, and the integrated value of the correction value P becomes the first threshold value (5% of the current SOC). The case where the full charge reset is executed when the value is reached has been described as an example. On the other hand, each time the current value is corrected based on the correction value P, the correction value P is subtracted (corresponding to the integration) from the initial value (for example, 5% of the SOC at a certain point in time), and the subtracted value (integration value). When the first threshold value (for example, 0%) is reached, a full charge reset may be executed.

15 Power storage device 30A Battery cell (an example of power storage element)
31 BMU (an example of management device)
33 Current sensor 33A Shunt resistance (example of resistor)
36 Temperature sensor 37 Management unit

Claims (11)

It is a management device for power storage elements.
A current sensor connected in series with the power storage element and
With the management department
Equipped with
The management department
A correction process that corrects the current value measured by the current sensor based on the correction value, and
An estimation process that estimates the state of the power storage element based on the current value corrected by the correction process, and an estimation process.
An integration process that integrates predetermined values according to the execution of the correction process, and
When the integrated value integrated in the integration process reaches the first threshold value, a reduction process for reducing the error accumulated in the estimated value of the state, and a reduction process.
A change process for changing at least one of the predetermined value and the first threshold value according to a physical quantity related to a change in the characteristics of the current sensor.
A management device that runs. The management device according to claim 1.
The predetermined value is the correction value.
The management unit is a management device that changes the correction value in the change process. The management device according to claim 1 or 2.
The management device, wherein the state is a charging state of the power storage element. The management device according to claim 3.
The power storage element is a management device having a plateau region in which a change in voltage with respect to a change in charge state is small. The management device according to claim 3 or 4.
The reduction process is a process of charging the power storage element to a predetermined charge state and updating the estimated value of the charge state estimated by the estimation process to the value of the predetermined charge state. The management device according to any one of claims 1 to 5.
The physical quantity is a current value measured by the current sensor, and is a current value.
The management unit is a management device that changes at least one of the predetermined value and the first threshold value when a current value equal to or higher than the second threshold value is measured by the current sensor in the change process. The management device according to any one of claims 1 to 6.
The physical quantity is a current value measured by the current sensor, and is a current value.
When the current sensor continuously measures a current value equal to or more than a third threshold value and less than a fourth threshold value for a predetermined time or longer in the change process, the management unit has at least the predetermined value and the first threshold value. A management device that changes one. The management device according to any one of claims 1 to 7.
A temperature sensor for measuring the temperature of the power storage element is provided.
The physical quantity is the temperature measured by the temperature sensor.
The management unit is a management device that changes at least one of the predetermined value and the first threshold value when a temperature equal to or higher than the fifth threshold value is measured by the temperature sensor in the change process. The management device according to any one of claims 1 to 8.
The current sensor has a resistor, and is a management device that measures a current value using the resistor. With a power storage element
The management device according to any one of claims 1 to 9,
A power storage device equipped with. It is a management method for power storage elements.
A correction step that corrects the current value measured by the current sensor connected in series with the power storage element based on the correction value, and
An estimation step for estimating the state of the power storage element based on the current value corrected in the correction step, and an estimation step.
An integration step that integrates predetermined values according to the execution of the correction step, and
When the integrated value integrated in the integration step reaches the first threshold value, a reduction step for reducing the error accumulated in the estimated value of the state, and a reduction step.
A change step of changing at least one of the predetermined value and the first threshold value according to a physical quantity related to a change in the characteristics of the current sensor.
Management methods, including.

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